It seems to me that the problem stems from you thinking communism necessitates authoritarianism.
It doesn't technically necessitate it, it just makes it very likely to happen, due to its insistence on there being only one political party. Communism isn't just an economic system, it's predicated on a government-run economy in a way that most other economic systems aren't.
Someone saying they are a communist would be the same situation as you saying you are a socialist
If they mean socialist, they should say 'socialist.' Most people understand this to mean that you're for things like free education, medical care, etc. When you say you're a communist, at least in the West, you're signifying to others that you either like or support governments like the USSR and CCP. I understand what you're saying about there being some overlap in the terms, but the main distinction to me is that communists believe in a single political party system of government, whereas socialists don't.
Because the US and other countries make such a point of preventing communism from succeeding, it can be frustrating when a lack of successful large scale communism is used as proof that communism can’t work.
While the U.S. has certainly put a lot into preventing communism from spreading, it hasn't always succeeded. I would argue that the communist states that do exist demonstrate its main problem quite clearly: a single political party system puts a government on the fast track to authoritarianism. Multiple political parties mean there is always an opposition to a government that becomes authoritarian; it's not a fool-proof defense against it, but way better than with only one party.
I have tried my very best to not make any assumptions about you, other than the political ideology you stated you had, but if I accidentally did, please tell me. I do not wish to offend you, and rather just want to provide my input on what you have said.
No, you didn't make assumptions, and I appreciate your cordiality.